Below is the list of root packages, download the package required for your device.
Xperia Arc:| | | | .
1. plug in your device to your PC / Mac
2. Copy the package to the fastboot folder*
(fastboot folder will appear if you have properly unlocked boot loader)
3. Open command prompt and move to the boot loader directory
4. type the required command and hit enter
fastboot flash system YOURDOWNLOADEDFILE.img
fastboot -i 0x0fce flash system YOURDOWNLOADEDFILE.img
fastboot-mac -i 0x0fce flash system YOURDOWNLOADEDFILE.img
Let the root process finish! and you’re device has successfully rooted.